Return a ContextInfo from Graphite's ContextFactory.

Previously, the context factory would return a tuple containing
pointers; this is brittle and makes it difficult to add elements
to the return type. Now it returns a named struct containing the
same information.

Change-Id: I4f1aa636b31704028bf6fbcb048a14dbc042c372
Bug: b/40044139
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/757116
Commit-Queue: Robert Phillips <robertphillips@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
6 files changed